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Verification of Boyles Law

المؤلف:  GEORGE A. HOADLEY

المصدر:  ESSENTIALS OF PHYSICS

الجزء والصفحة:  p-178

2025-11-12

478

•  For Pressures Greater than One Atmosphere. - Demonstration. - Bend a glass tube as shown in Fig. 1, the long arm being open and the short one closed. Fix this to a vertical support and place a graduated scale between the two arms. Pour mercury into the long arm by means of a long funnel, and tip the tube in such a way as to let bubbles of air pass from the short tube into the long one, and thus bring the mercury to the same level AB in both. This line is chosen at a convenient position, say 20 cm. below the closed end. On pouring mercury into the long tube, it will be found necessary to fill it to a height of about 760 mm. above the mercury in the short tube to reduce the volume of the gas one half. The pressure upon the mercury in the short tube is the elastic force of the air above it, and this is equal to the pressure above the line C'D in the long tube, which is two atmospheres, one being the 760 mm. of mercury and the other the free atmosphere above it. State how this proves the law. 

•  For Pressures Less than One Atmosphere. - Demonstration. - Fix vertically a glass tube closed at the lower end, about 70 cm. long and at least 8 mm. in internal diameter. Cut off a piece of glass tubing 6 or 7 mm. in external diameter and make three marks upon it, one at 10 cm., one at 20 cm., and one at 58 cm. from one end. Pour mercury into the large tube until, on thrusting the smaller tube into it with the 10 cm. mark uppermost, the mercury will rise to the 10 cm. mark. Place the finger over the top and enclose a column of air 10 cm. long. This has an elastic pressure of 1 atmosphere and just balances the pressure on the surface of the mercury in the larger tube. Now raise the smaller tube until the mercury sinks to the 20 cm. mark on the inside of the tube; ….

FIG.2.